Displays a standard "Open" windows dialog box.
It does NOT open a file; it just allows the user to select the desired file using a Graphical User Interface.
filename input is used to set the defaults of name, directory and/or extension.
The output is the fully-specified file name that the user selected.
If the user presses "Cancel", then DIALOGFILEOPEN outputs the empty list (
filename input must be a word that specifies the directory to start in, the default filename, and/or extension of the filename.
Wildcard characters ("*") are permitted as the filename or extension.
SHOW DIALOGFILEOPEN "|c:\\Program Files\\FMSLogo\\Examples\\Windows\\*.lgo|
The dialog box shows all files ending in ".lgo" in the specified directory.c:\Program Files\FMSLogo\Examples\Windows\Visual.lgo